With his coming testimony before the US Senate in mind, November's Nato conference in Lisbon and Obama's strategic review of the surge in December, Petraeus probably had deeper campaign objectives too. "ISAF headquarters have made it clear that we shouldn't get ahead of the success curve with the media," said a leading US figure in southern Afghanistan.

So the focal point of the autumn surge in Kandahar province, though incorporating double the number of Afghan security forces used in Marjah and only slightly fewer coalition forces — nearly 20,000 soldiers — was conducted with little fanfare. In turn, Petraeus's reticence concealed a greater truth that has only recently begun to emerge. Behind the contrived silence of Nato commanders, and unnoticed by a British public who are at best baffled by the Afghan war, at worst appalled by it, the surge is opening up the campaign and killing Taliban. So far as it can, the surge is working.

The metrics in measuring success in any counter-insurgency are murky and imprecise. Given the seasonal variations in Afghanistan's war, whereby winter and poppy harvest are traditional low points in enemy activity, short-term interpretation becomes even less reliable. Days short of leaving Afghanistan, General Carter, the architect of so much of the surge operation in the south, spoke only of "encouraging signs" rather than "winning", and warned against judging the effect of the surge until next summer when the new fighting season arrives. "They are by no means huge measures of success," he cautioned at the end of October, describing an increase of local intelligence given to Nato by Afghans and an improvement in the security along Highway 1 and other roads, where Taliban attacks decreased by up to 80 percent as the surge intensified. "But you can see the general direction of travel."

Yet other leading figures involved with the war in the south — less beholden to the directives of higher command — spoke privately, in detail and with confidence of the Taliban being "routed".

"The Taliban are getting an absolute arse-kicking," said one top-level Westerner deeply involved with operations in Kandahar. "We're taking them off the battlefield in industrial numbers. We're convinced that the initiative has really shifted."

Ahmed Wali Karzai, the brother of the Afghan president, the most powerful Afghan in the south and probably the best informed, went further still. "The Taliban are broken and defeated here," he told me in October, a few months after Petraeus, among others, decided that it was better to preserve him as an ally rather than attempt to sideline or undermine him. Once the subject of a barrage of allegations, Ahmed Wali Karzai has a new image typical of others among the war's changes. Nato has stopped chastising local villains. Now it is embracing them as part of the solution, citing "gangs and counter-gangs" as the way ahead, believing it can change bad actors into good as a way of combating the Taliban and stabilising the country, a policy shift that is long overdue.

"They are in a miserable state," Karzai added. "Their best commanders are all dead and their fighters run here and there. Their casualties are high and they can barely fight."